Two wheat (Triticum aestivum L.) cultivars with different drought tolerance (the drought-tolerant HF9703 and the drought-sensitive SN215953) were used to examine the effect of exogenous glycinebetaine (GB) applied to root system on the drought tolerance of wheat seedlings. The results showed that GB treatment can ameliorate the water status of the wheat seedlings under water stress. The GB-treated seedlings maintained higher water potential (ΨW), turgor (ΨP) and relative water content (RWC) than untreated seedlings, which were ascribed to the improved osmotic adjustment (OA) caused by the enhanced accumulation of soluble sugars and free proline. Exogenous GB could improve the anti-oxidant en-zyme activities in wheat seedlings under water stress. The GB-treated seedlings had higher SOD, APX and POD (but not CAT) activities and lower MDA content than controls. It was concluded that the exogenous GB could improve the drought tolerance of wheat seedlings by ameliorating the water status through improving the OA and anti-oxidant enzyme activities. Our results also showed that the drought-tolerance cultivar maintained a better water status and higher anti-oxidative enzyme activities than the drought-sensitive cultivar after water stress, moreover, exogenous GB had a more significant effect on ameliorating the water status of drought-sensitive cultivar than that of the drought-tolerance cultivar while there was no difference in the effect of exogenous GB on the improvement of anti-oxidant enzyme activities between two cultivars.%研究了外源根施甜菜碱对抗旱性不同的两个冬小麦品种幼苗抗旱性的影响.结果表明,水分胁迫会诱导小麦幼苗体内甜菜碱的积累,外源甜菜碱能提高体内甜菜碱含量,改善水分胁迫下两小麦品种的水分状况,提高其水势、膨压和相对含水量,这可能是通过提高小麦幼苗体内一些有机渗透调节物质(如可溶性糖和脯氨酸)含量进而增强其渗透调节能力而实现的.甜菜碱还能提高水分胁迫下幼苗体内SOD、APX和POD活性,而对CAT活性无影响.水分胁迫后,甜菜碱预处理的幼苗叶片丙二醛含量低于未处理幼苗,表明外源甜菜碱能缓解水分胁迫引起的膜脂过氧化.结果还表明, 水分胁迫后,抗旱性品种的水分状况和抗氧化酶水平优于水分敏感型品种,外源甜菜碱在改善水分胁迫下的水分关系方面对水分敏感型品种效应更大,而在提高抗氧化酶活性方面对两品种无明显差异.
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